ASSUME
by RBnC
Summary: The Nogitsune tricks Derek into thinking he's having sex with Stiles. Only, plot twist: Derek knows it's the Nogitsune but he just wants to sleep with Stiles, even if only once and he might not ever get the chance. Read to find the second plot twist. IS BEING A BUTT. THE TITLE IS SUPPOSED TO BE ASS U ME BUT, NO THEY'VE GOT TO BE BUTTS.


When someone enters the loft, Derek knows immediately. It's not the alarm that's connected – which isn't even turned on, smart, Derek, really smart – to the door, it's the smell that comes wafting in. It's Stiles' scent. Or the Nogitsune. He'd gotten an explanation about how there were two Stiles' running around now and he had to be informed about that in case he ran into him. Which, did Scott really think he'd throw his guard down if the Nogitsune acted like Stiles and cried a bit? Okay, he totally would, but that's beside the point.

He knew that Stiles was supposed to be with Scott at his house, which meant that the thing entering the loft's living room had to be the Nogitsune. Derek descends the stairs, more cautious than he has to be, but less cautious than he normally is.

"Hey, I didn't know if you'd actually be here." Stiles – the Nogitsune – smiles and shuffles awkwardly.

"What do you want?" Derek snaps, glaring at the thing wearing Stiles' face.

"I wanted to be around someone." It looks away and Derek think's it's actually pretty convincing, "Scott left to go do something. He didn't give an explanation."

Derek decided to play along, "How'd you get here?"

"I drove Roscoe." It takes Derek a second to remember that's what Stiles' Jeep is called.

Which is ridiculous, that's the name of a dog, not a car.

"Your dad let you drive?"

"He's at the station."

There's a long, tense silence as the Nogitsune shuffles, rubbing his hands together.

Derek sniffs the air silently, noticing all of the underlying smells that go with the fox in front of him. The most prevalent is death. Something inside Derek twinges because Scott had told him about that part, too. About how Scott thinks Stiles is dying and it might be connected to the Nogitsune.

"Why are you here?" Derek asks, fed up with the trickster's ploy.

"I didn't want to be alone and I figured you were here alone, too." Derek hears the tick in its heartbeat that usually indicates a lie.

"Why are you really here?" Derek growls.

The Nogitsune shuffles a bit, not meeting Derek's gaze. He'll give it points for sticking this through.

"I don't want to be alone and…" It swallows thickly, shuffling some more.

"And what?"

Derek tenses when it steps closer to him.

"I know you talked to Scott. Did he tell you that I'm dying?"

Derek doesn't know where it's going with this.

"Yes. Doesn't matter, I can smell it on you."

"I don't want to die, Derek. And I really, really don't want to die without…" He looks away and runs a hand through his hair.

It looks at Derek as if weighing some heavy decision in his mind before sighing, with its full body just like Stiles does, and stepping just a bit closer to Derek.

The former Alpha doesn't know if he should be worried at the proximity of the trickster fox.

It sighs before bluntly stating, "Since I'm dying, I figured I might as well give the one thing I want most a shot."

Derek keeps his face neutral as he tries to figure out what it meant.

It rolls its eyes before stepping forward and kissing Derek full on. His lips are cold, almost as cold as the hands holding the sides of his face. It tastes like copper and death and Derek quickly pulls away.

"What the hell!?" Derek growls, flashing his eyes.

He knows it's not as intimidating as his old Alpha red's but they work just the same.

"I – I'm sorry! It's just. I'm dying. No matter what Scott says, I'm thinking the only way for us to kill the Nogitsune is for me to die and I'm alright with that. I just…I didn't want to die knowing I never even tried with you. I'm sorry."

Derek doesn't know how to respond to that so they stand in uncomfortable silence.

The Nogitsune knows he has feeling for Stiles. Derek knows that Stiles has feelings for Lydia. The Nogitsune should know that Stiles has feelings for Lydia. He's just doing this to fuck with Derek.

Derek growls when it starts to walk away.

"And what were you expecting to happen? I'd just kiss you? Fuck you? Let you go off to die? Is that what you're expecting?"

"Honestly? Yes. But I guess that's too much like a bad porno. I mean, if you don't want me…if you don't feel anything for me I don't want you to. I just. I guess this is for me. I don't want to die knowing I hadn't tried." He looks at Derek like he's sad.

Derek wonders about the merits of fucking a Nogitsune. THE Nogitsune. There's obviously another side to this. A side that's meant to hurt Derek or manipulate him into something. But if Stiles really is dying…this could be his only change at anything resembling something real with Stiles.

He can't be like Scott and think they'll all get out of this alive. It's just not in him. Not after he's lost everything else.

He wonders if it'll be worse when he loses Stiles.

"Sorry for bothering you." It comments, chuckling lowly just like Stiles does.

He doesn't even look steady on his feet as he makes his way to the barely open front door.

Derek thinks that if this is the Nogitsune and it does use this to manipulate him, he can just deny it. Can't he? Who would believe he fucked Stiles through the mattress? Especially with him looking like walking death. And if it kills him in his sleep, at least he'd go out with a semi-smile on his face.

Derek stalks forward, saying fuck it.

It looks surprised when Derek spins it around and kisses it.

It's rough and fervent and not at all how he wants to kiss Stiles. But this isn't Stiles.

If he's going to do this, he'll pretend it is the rambunctious ball of energy.

It – Stiles – wraps his arms around Derek's neck immediately, kissing back as heatedly as Derek had started with. Stiles makes a noise, not unlike a squeak, when Derek wraps his arms around Stiles and lifts him up off the ground and into his arms.

Stiles' legs immediately wrap around Derek's waist, though that's more for show with how weak they're wrapped around him. Derek keeps his hands on Stiles ass as he continues kissing him.

Eventually Stiles pulls away, shaking in Derek's arms. Derek just looks at the Nogitsune and wonders if he should really be doing this. If he doesn't do this now, he may never get another chance.

"What changed your mind?" It asks, trying to get its shaky breathing under control.

Derek wonders how he should reply before deciding to go with semi honesty, "I guess I'd hate for you to die without trying, too."

It looks a little shocked and Derek has to give it credit for still sticking to this.

The brunet leans in, kissing Derek heatedly, and moves his hands from the Beta's shoulders to thread through the hair on the nape of his neck. It still tastes like copper and death, but Derek brushes that aside and he winds his arms underneath Stiles' ass, holding him closer.

It's not long before Stiles is pulling back again, shaking like a leaf in a hurricane, and Derek wonder how far it's willing to take this.

"What's wrong?" Derek asks, nosing at its jawline.

"Jus'…um…dizzy." He replies, leaning his head to give Derek more access.

"Should I stop?" Derek teases before nipping at Stiles' jaw.

"No, god no. Just… 'm cold."

"I can feel that." Derek intones, smirking.

His hands are, in fact, like ice on the back of his neck. Instead of putting the brunet in his arms down, he carries him over and up the stairs which lead to his room.

Derek doesn't have time to think about the fact that the Nogitsune is the first person who's been in this room. He honestly doesn't want to think about it.

The Beta gently sets Stiles on the end of his bed and kisses him again, slow and chaste, before licking his way inside its mouth. He presses forward, effectively herding it to the base of his bed and pinning it there with his hands on the brunet's hips. Derek jumps a bit when its hands worm their way under his shirt. He quickly pulls them out and places them between his own, trying to warm them up.

"I'm not gonna get warmer, Derek." It smirks before it falls from his face, "Sorry."

Derek rolls his eyes before getting up, off the bed, and making his way over to his closet. He has a large comforter in there that he never uses because of his naturally high core temperature, but he figures with the Nogitsune as cold as an ice cube, he can stand it.

He comes back to his room to find it scooting towards the end of the bed as if to get up.

"What are you doing?" Derek asks, raising an eyebrow.

"Uh…nothing, I guess. I thought you'd changed your mind." It looks at the comforter weird, as if it wouldn't have expected that in a million years.

"It's green."

Derek rolls his eyes again before climbing back on the bed and wrapping the brunet up in the fluffy blanket and kissing him again, "I know it's green."

Between kisses it gets out, "I wouldn't think you'd own anything with color."

"Shut up." He doesn't mean to growl, but he does.

"Did you just -" Derek kisses him, deep and warm, and he can't get noise out.

Derek quickly undresses himself and the Nogitsune, sending their clothing to all corners of the room. Really, Derek doesn't know how Stiles does it. Most people look bulked up with clothing on and they're thinner while naked, but the body beneath him is toned and there's plenty of muscle. Not what he'd expected Stiles to look like when naked, and he'd given it quite a bit of thought.

So he goes about memorizing Stiles body with his hands and lips, making sure to never be too rough with the shaking body beneath him. It's not shocking that the brunet beneath him never stops talking, even in the midst of this. He mutters encouragements and praises while he runs his hands all through Derek's hair and over his shoulders and chest.

It doesn't take too long for the praise and encouragement to turn into pleading. He'd never be able to deny Stiles anything if he'd just keep asking in that voice. Derek reaches into his nightstand drawer for the three month old bottle of lube that's been sitting in there untouched. Derek briefly wonders if lube can actually expire before focusing on the brunet underneath him.

And it's a wonderful sight.

He's flushed, with slightly swollen lips and disheveled hair. Derek doesn't think he's ever found someone more attractive.

"I don't have a condom," Derek confesses, because really, he hadn't planned on getting laid any time soon.

"Don't care." It breathes, looking at Derek like it wasn't to devour him whole.

Derek leans in and kisses the boy beneath him, pressing one finger inside of him. The brunet beneath him keens, his grip on Derek's shoulders tightening. Derek concentrates on kissing and nipping down Stiles jawline as he stretches him out. One finger eventually leads to two which leads to three and really Derek is just enjoying the sounds coming from the body below him to think about moving on.

"Derek," The brunet breathes, shaking all over, "Please, Derek, fuck me."

Derek smirks as he bites the brunet's neck a bit harder than he ought to and continues fingering his current lover.

Is that the word for this? Lover?

Sounds as good a word as any.

"Derek, Please, jus-" he interrupts himself with a wanton moan, "Just – Please."

"I'm enjoying myself," Derek teases, purposefully hitting Stiles' prostate and making the brunet shiver.

"You ass." It breathes, breath hitching when Derek repeats his last motion, "I won't break if you fuck me, Derek."

"I'm not worried about that. I know you can take anything I give you."

"So you're being a tease?" Gorgeous eyes stared down at him, incredulously.

Derek kisses the spot where Stiles' leg meets hip and grins, "Perhaps."

"Just…please." It moans, trying to get Derek to move or do something. "It's not enough."

"I could spend all night here. Can't you?"

The brunet smacks his head back against the pillow and before Derek knows what's happening, he's jumping away from ice cold feet against his bare back.

"Fuck!" Derek shouts, grabbing the cold foot trying to press against him again.

Stiles grins at him, licking his lips, "Are you going to fuck me now?"

"Impatient." Derek grabs his bottle of lube and applies a generous amount.

"Yes, I am very impatient, considering I've wanted you to do this to me since you threw me up against the wall of my bedroom."

"That was two years ago."

Stiles nods, looking like the cat who got the cream.

"If you don't start fucking me soon, Derek, I'm going to get you again," The brunet threatens playfully.

Derek rolls his eyes before he kisses the smug bastard. As he licks his way inside his mouth, Derek pushes inside the younger man. And if Derek though he liked the sounds earlier, he was in love with the sounds it was making now.

And as much as he wants to let his instincts take over and fuck into Stiles furiously, he stills once he's fully inside the teenager. He waits until the brunet rocks against him to pull out ever so slightly just to push back in.

He starts a slow, languid pace to fuck Stiles with. It's fine for a while with the brunet letting out cut-off whines and moans. Then he starts begging for Derek to fuck him harder, faster. So Derek bites Stiles' neck, not hard enough to pierce, but definitely hard enough that it'll leave a visible mark.

And Stiles lets out the _filthiest_ moan for it.

Derek picks up the pace, but just a bit, and he reaches down to wrap his fingers around Stiles' cock. He starts stroking it slowly and he almost loses what little self-control he has left when the brunet starts moaning and thrusting into the Beta's hand for just a bit more friction.

The younger man doesn't last much longer and Derek doesn't last much longer than that with the way the brunet is clenching around him. Derek's body is shaking, but not nearly as bad the body beneath him.

As much as Derek would love to stay where he is, resting on top of the boy beneath him, he rolls himself over so he's on his side facing the brunet.

He probably should have thought this whole things through a bit more, but as the brunet rolls over to lay halfway on top of Derek, he finds himself not really caring. It turns so he's got the brunet lying halfway on top of him and the large comforter is sort of thrown haphazardly over the both of them.

Derek think's it would be smart to stay awake with the trickster spirit in his bed, but by the time that thought crosses through his mind, he's practically asleep.

When Derek wakes up, it's to the sound of his phone going off repeatedly. Derek is warm and content and so he decides to ignore the phone until he remembers what's going on in his life. Derek sits up in his bed, slightly confused when he has to fight the comforter that's usually stored in the closet. He grabs his cell from his pants pocket, blearily wondering why they're on the floor and he's naked.

He answers the phone as he turns around and it's like getting hit with cold water in the face.

But why is it still in his bed?

Derek snaps out of it as Scott's worried voice buzzes across the line, "Derek! For the love of god, I need your help! Stiles is missing again and I have no idea where he'd be. I was gone for like two hours and he's gone now! Like gone, gone!"

Derek tries to reign in his panic and surprise at Scott's freak out.

"Scott calm down, Stiles is here. With me. He's fine, he's sleeping."

"No, 'm not," Stiles mumbles into his pillow.

"Okay, so not sleeping."

"What is he doing at your place?"

"He said he didn't want to be alone."

Scott sounds absolutely pissed when he tells Derek to put Stiles on the phone. Derek complies because Scott is the Alpha and even if he doesn't consider Derek his Beta, Derek has to follow. It's a compulsion he'd almost forgotten about.

Stiles grabs Derek's phone without moving from his resting spot with his face pressed into Derek's pillow.

Derek allows himself to rethink the events of last night with the knowledge that he'd actually slept with Stiles. That Stiles had wanted him and that this wasn't some sick game. Derek doesn't even know what he's doing as he listens o Stiles talk to Scott.

"Scott calm down, I left you a note and everything."

"No, you didn't!" He hears Scott call from the other end of the line.

"Yes, I did. It's on the living room table where I was resting before you left."

"I didn't see any kind of – oh."

"Yeah, oh."

"Well now I feel like an idiot."

"You're not an idiot, Scott. Just not observant."

"Should I come over or?"

"Nah, I'll be back later. Maybe with Derek." Stiles chuckles at Scott's confused noise before saying goodbye and hanging up.

"So." He tosses Derek's phone to the end of the bed.

"So." Derek mimics.

"You wanna talk about last night or do you want to try and warm me up again?" The smiles he throws Derek's way is adorable and Derek has to turn his head so he doesn't actually go with the second option.

"Shut up, Stiles."

"Oh, good. You do remember my name. I was worried you'd forgotten while we were having sex. I've had a lot of fantasies about you moaning my name."

"Oh, my god. Stiles, _shut up_."

"Come here and make me."

So he does.


End file.
